The Gray Bulb-Rot of Tulips 



11 



Muscaria botryoides. Narcissus poeti- 

 cus, Galanthus nivialis, and Crocus 

 vernus, except in one case on the 

 last-named species. Ritzema Bos 

 (1903 a: 181) observed severe losses 

 in iris, hyacinth, and gladiolus in 

 the field, which he attributes to this 

 fungus. 



Westerdijk (1911:26), who grew 

 tl is fungus in pure culture, records 

 failure to obtain infection of the 

 roots of beets, carrots, and potato 

 tubers by inoculation in moist cham- 

 bers in the laboratory, although it 

 readily attacked tulip and hyacinth 

 bulbs under the same conditions. 

 She obtained infection with it in 

 one case on onion bulbs. 



Figure 2. branching tip of rapidly grow- 

 ing MYCELIUM IN POTATO AGAR, PETRI-DISH 

 CULTURE 



The mycelium is filled with densely granular proto- 

 plasm 



Life history 

 All the evidence from the work of 



previous investigators and from the 



authors' researches indicates that 



this pathogene depends upon its sclerotia to tide it over from one season to 



the next. Mycelium which is readily produced from the sclerotia, spreads 

 through the soil and attacks the suscept. The 

 pathogene appears to be a low- temperature para- 

 site, its attack on the bulbs occurring late in the 

 fall or during the mild weather of winter and early 

 spring. Diseased bulbs always show a well-devel- 

 oped root system which is rarely affected. The 

 attack apparently occurs at the nose, or tip, of 

 the bulb as the shoot begins to protrude from the 

 fleshy scales. Because of the restricted range of 

 suscepts, the disease may be expected to become 

 serious only in soils repeatedly planted to tulips. 

 Since affected bulbs are usually more or less 

 completely destroyed before digging time, and 

 since the sclerotia are largely produced in the 

 soil around diseased bulbs, the chances of its 

 rapid dissemination are slight. 



Figure 3.' branching and 

 anastomosing mycelium 

 in old culture on po- 

 tatoJagar 



Barrel-shaped cells entirely 

 empty; protoplasm of main 

 branch containing granular vac- 

 uolate protoplasm 



CONTROL 

 In order to exclude the pathogene from uncontaminated areas, it is 

 important to know in what manner it is transported from one locality 



